[Heathkit] Off Topic Help re: volume on/off pot for HTX-100

[OTAKEBI at aol.com]

Have a Realistic HTX-100 10 meter mobile that has a bad on/off volume  pot.
I have the pot out and it is broken.
Called Mouser and they have no such ALPS part number.
They cross checked with ALPS.
The number on the pot is Alps 863F 50KA.
Has anyone had to replace one of these and what part number did you find or  
sub did you use?
I know that another brand will work the problem is I can't eyeball the size  
of the other brands and I do not want to order without being in the ball  park.
Thanks for any help,
Dan N4VET